1. Field of the Invention
The present invention relates to a communication apparatus, and more particularly, to a communication apparatus with echo cancellation.
2. Description of the Prior Art
A full duplex communication of an Ethernet network is accomplished by four unshielded twisted pairs (UTP). Thus, a transport port can have four channels. For the most part, the transmitted signals of a channel, (i.e. an unshielded twisted pair), at its transmitter are interfered with by an Echo formed at its receiver, and the transmitted signals of the transmitter are also interfered with by near-end cross talk (NEXT) formed at the other receivers. When processing digital signals of the receivers, the interference must be eliminated.
A conventional technology has already been disclosed in U.S. Pat. No. 7,333,603. In this conventional technology, it adjusts resistors and capacitors by using error information of a data slicer. Since the signal processed by the data slicer gathers all the error information together, the signal must be first converted before using it. That is, the signal outputted by the data slicer blends too much noise and error and it is too difficult to be used, which may result in distortions easily. Moreover, although the conventional technology can eliminate the echo signal returned to the receiver as far as possible, it cannot control the echo component returned to the receiver to the smallest and cannot control the transmitting power of the transmitter.